1. Field of the Invention
The present invention relates to a developing device for developing an electrostatic latent image on an image carrier with a one-component developing agent and an image forming apparatus equipped with the developing device.
2. Description of the Related Art
As a developing device utilized for an electrophotographic apparatus and electrostatic recording apparatus to visualize an electrostatic latent image, a two-component developing system has currently been employed which magnetically feeds a two-component developing agent, that is, an agent composed of a colored particle called a toner and a magnetic particle called a carrier. It effects development, under an electrostatic force, with the agent attached to an electrostatic latent image.
In the two-component developing system, the developing device has the drawback of being bulkier and complicated, and there is a need to control the toner/carrier mixed ratio. The recent major trends in small type copiers and small printers has been toward the use of a one-component developing system requiring no carrier.
Of these developing devices, a developing device using a one-component non-magnetic developing agent does not need an expensive magnet roller as a developing agent holding member, thus readily achieving a compact, light-weight and low-cost unit.
For an elastic roller made up of a developing agent holding member, it is possible that, even if the developing agent holding member is set in contact with an image carrier, it causes no injury to the image carrier. Hence an associated developing electrode can be placed nearer the electrostatic latent image. It is, therefore, possible to improve the sharpness of character and line images and to effect development of high image quality.
In spite of such advantages, when feeding is effected with the developing agent formed, as a thin layer, on the surface of the developing agent holding member, a print pattern hysteresis prominently emerges due to a charge difference between a printed and a nonprinted area at those previous printing times, causing an adverse effect on an image at the subsequent developing time.
Further, the feeding of the developing agent has to be effected under those physical and electrostatic forces across the developing agent and the developing agent holding member and, when continuous printing is performed, there occurs a drop in holding power of the developing agent, thus causing the flying of the developing agent and the contamination of the developing device.
The conventional developing device using a one-component-based developing agent is compact, light in weight and low in cost, but it involves a drop in quality of an image caused by a print pattern hysteresis built up at a previous copying cycle as well as the flying, etc., of the developing agent upon copying in a continuous mode.